JP2815066B2 - Cooling structure of 4-cycle engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for a four-stroke engine, and more particularly, to a cooling structure for a two-stroke engine having two exhaust ports per cylinder. The present invention relates to improvement of a jacket shape and the like that can be secured.

2. Description of the Related Art For example, in a SOHC engine in which intake and exhaust valves are driven by a single camshaft, when two exhaust ports are provided for each cylinder, when two exhaust ports are provided in a direction perpendicular to the camshaft, the two Generally, a structure is provided in which a spark plug insertion hole is formed in a portion, and the spark plug insertion hole is inclined outward substantially parallel to the exhaust valve when viewed in the camshaft direction. As a cooling structure in the vicinity of the two exhaust ports in such a four-cycle engine, as conventionally described in, for example, U.S. Pat. No. 4,714,058, between a peripheral wall of each exhaust port and a peripheral wall of a spark plug insertion hole. There is a structure in which a communication space for flowing cooling water to the intake port side between the two exhaust ports is provided. In this conventional cooling structure, since cooling water flows through the portion between the exhaust port and the peripheral wall of the ignition plug insertion hole, the cooling property of the portion can be ensured and the durability can be improved.

[Problems to be solved by the invention]

By the way, in order to increase the speed and performance of the engine, it is necessary to increase the diameter of the exhaust valve in order to improve the exhaust efficiency, and accordingly, the exhaust port also increases in diameter. In this case, depending on the diameter of the exhaust port, it is impossible or extremely difficult to secure a communication space between the peripheral walls of both exhaust ports and the peripheral wall of the spark plug insertion hole as in the above-described conventional structure. Become.

On the other hand, even if the diameter of the exhaust port is considerably increased, since there is a relatively large space between the exhaust ports, it is possible to form a water cooling jacket between the two ports. However, even if a jacket is simply formed between the two ports, the cooling water only accumulates in the jacket and does not flow through the jacket, so that improvement of the cooling effect cannot be expected only by forming the cooling jacket.

In view of the above, the present invention has been made in view of the above-described conventional situation, and is capable of securing the flow of cooling water between both exhaust ports even when the diameters of both exhaust ports are increased, and improving the cooling effect. The purpose of the present invention is to provide a cooling structure.

[Means for solving the problem]

The present invention cools the vicinity of the ignition plug insertion hole and the exhaust port of an engine having two exhaust ports per cylinder and having an ignition plug insertion hole formed between the exhaust ports when viewed in the direction perpendicular to the camshaft. In the cooling structure for the exhaust port, the exhaust port is viewed in a cross section parallel to the camshaft and the cylinder axis at a portion surrounded by the exhaust port, the ignition plug insertion hole, and the outer wall of the cylinder head. An interport jacket is formed so as to be located at the center of the cylinder head and to extend upward from the mating surface with the cylinder body to at least near the top wall surfaces of the two exhaust ports, and the mating surface of the cylinder head and the bottom surface of the exhaust port are formed. And a pair of left and right communication passages for communicating the jacket between the ports with the main jacket surrounding the upper surface of the combustion chamber is formed.
A cooling water introduction passage opening at the mating surface of the cylinder head is erected at the center of the inter-port jacket, and the cooling water introduction passage is extended to at least the height of the center of the exhaust port. Introduced into the upper part of the inter-port jacket through the cooling water introduction passage,
It is characterized in that it descends from the upper part along the side surfaces of the left and right exhaust ports, and flows to the main jacket through the left and right communication passages.

[Action]

According to the cooling structure of the four-cycle engine according to the present invention, the cooling water is introduced from the cylinder body side through the introduction passage into the upper portion of the inter-port jacket, and from the upper portion, the side surfaces of the left and right exhaust ports. And flows through the left and right communication passages to the main jacket, so that the cooling performance in the vicinity of the exhaust port and the spark plug insertion hole can be ensured.

In the present invention, the cooling water introduction passage is erected so as to extend to the upper part of the inter-port jacket, and the flow of the cooling water is secured by a structure only forming the communication passage. There is no need to provide a space in the part between the insertion hole peripheral wall and ensure the flow of cooling water,
As compared with the conventional structure in which the communication space is formed, there is more space in the formation of the exhaust port, the diameter of the exhaust port can be increased, and high speed and high performance of the engine can be supported.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 8 are views for explaining a cooling structure of a four-stroke engine according to an embodiment of the present invention. FIG. 1 is a right side view in cross section of a cylinder head, and FIG. 2 is a view of FIG. FIG. 3 is a cross-sectional plan view of the cylinder head, FIG. 4 is a plan view of a valve operating mechanism portion of the engine of the embodiment, FIGS. 5 and 6 are VV of FIG. Line cross section, VI-VI
7 is a bottom view of the cylinder head, and FIG. 8 is a right side view of the motorcycle equipped with the engine of the embodiment. 1, 4 to 6 and 8, the right side in the drawing, the upper side in FIG. 3, and the left side in FIG. 7 are the front of the vehicle, respectively. The description will be made while looking forward.

In the drawing, reference numeral 1 denotes a motorcycle on which the engine of this embodiment is mounted, and a body frame 2 of the motorcycle 1 has a main pipe 2b and a front end of a down tube 2c welded to an upper part and a lower part of a head pipe 2a. It is a so-called diamond type which is connected by welding the upper end of the sheet pillar 2d to the rear end of the main pipe 2b. In addition, 2g is an under guard for protecting the crankcase, 2e is a support pipe for the engine suspension bridged in the middle of the main pipe 2b and the down tube 2c, and 2f is a seat rail.

A front fork 3 for supporting the front wheel at the lower end is supported on the head pipe 2a so as to be steerable left and right. A rear arm 5 for supporting the rear wheel 4 at the rear end is vertically mounted on the seat pillar 2d. It is pivotally supported. Also this rear arm 5
Is connected to the vicinity of the rear end of the main pipe 2b via a link mechanism (not shown) and one shock absorber 8. Reference numeral 6 denotes a fuel tank, 7 denotes a seat, 9a denotes an air scoop that covers a side surface of the tank, 9b denotes a side cover that covers a lower portion of the seat, and 9c denotes a rear cover that covers a rear portion of the vehicle.

An engine unit 10 is suspended and supported in the vehicle body frame 2. The engine unit 10 is a water-cooled four-stroke single-cylinder engine, and has a structure in which a cylinder body 12, a cylinder head 13, and a head cover 14 are slightly inclined forward and stacked on a front upper surface of a crankcase 11.
One combustion chamber wall surface 13a is recessed substantially in the center of the lower surface of the cylinder head 13. The wall 13a forms a combustion chamber 15 with the head of a piston (not shown) slidably inserted into the cylinder liner 12a of the cylinder body 12.
A plug screw hole 13b for mounting an ignition plug is formed at substantially the center of the combustion chamber wall surface 13a, and the plug screw hole 13b is formed by the plug insertion holes 13c and 14a formed in the cylinder head 13 and the head cover 14. Is drawn outward so as to be inclined toward the exhaust side (front side). An ignition plug 16 is screwed into the plug screw hole 13b. Furthermore, left and right drain holes 13j and 13i communicate with the plug screw hole 13b, and the left drain hole 13j is connected to the connection pipe.
It is led out to the outer wall of the chain room 13h via 13k.

Left, center, and right intake valve openings 17, 18, and 19 are provided on one side of the combustion chamber wall 13a of the cylinder head 13 across the plug screw hole 13b, and left and right exhaust valves are provided on the other side. Valve opening 2
The plug insertion hole 13c extends upward between the left and right exhaust valve openings 20, 21 in the plug insertion hole 13c. The left intake valve opening 17 is led to the rear wall of the cylinder head at a left intake port 22 extending rearward of the vehicle so as to be substantially orthogonal to an axis of a cam shaft 42 described later in plan view. 18 and 19 are led out rearward by a central intake port 23a extending rightward in the vehicle width direction with respect to the camshaft 42 and a right intake port 23b extending substantially perpendicular to the camshaft 42.
The joint intake port 23 extends rightward in the vehicle width direction as a whole. The left and right cab joints 24 and 25 connect the left and right cab joints 24 and 25 to the rear end openings of the left intake port 22 and the merged intake port 23, respectively.
Right carburetors 26 and 27 are connected.

The left and right exhaust valve openings 18 and 19 are led out to the front wall of the cylinder head by left and right exhaust ports 28 and 29 extending in the shape of a letter and extending in front of the vehicle. The left and right exhaust pipes 31, 32 of the device 30 are connected. The two exhaust pipes 31, 32 are connected to the down tube 2c described above.
After passing through the left and right sides of the vehicle, it is bent to the right side, merges here, and extends rearward of the vehicle. A muffler 33 also serving as a back stay is connected to the extended end.

The left, center, and right intake valve openings 17, 18, and 19 have valve plates 34a, 35a, which open and close the left, center, and right intake valves 34, 35, 36, respectively.
In the left and right exhaust valve openings 20 and 21, valve plates 37a and 38a of left and right exhaust valves 37 and 38 for opening and closing the same are disposed, respectively. The valve rods 34b to 38b of the valves 34 to 38 pass through the ceiling walls of the intake and exhaust ports 22, 23a, 23b, 28, and 29 and protrude upward from the mating surface of the cylinder head 13.

Here, the valve rods 37b, 38b of the exhaust valves 37, 38 are perpendicular to the cam shaft 42 when viewed from a plane, that is, parallel to each other,
When viewed in the direction of the camshaft 42, they are inclined forward at the same angle and overlap each other. Each of the exhaust valves 37 and 38 has an urging spring interposed between an upper stopper 39 fixed to an upper end thereof and a lower stopper 40 disposed on a spring seat of the cylinder body 13.
The opening 41 is urged to close the openings 20 and 21 by 41.

The valve rods 34b to 36b of the intake valves 34 to 36 also form a right angle with the camshaft 42 in a plan view, and when viewed in the camshaft direction, the left and right intake valves 34 and 36 correspond to the exhaust valves 37 and 38, respectively. They are inclined backward at substantially the same angle and overlap each other. Also, the stem 35 of the central intake valve 35
b is arranged in a more upright state than the left and right intake valves 34,36. The upper ends of the left and right valve stems 34b, 36b are located above the upper end of the valve stem 35b of the middle intake valve 35, and the intersection C of these axes A, B is located at a high position on the left, right. It is located further above the upper ends of the valve stems 34b, 36b. Each of the intake valves 34 to 36 is urged in the closing direction by an urging spring 41 provided between the upper and lower stoppers 39 and 40.

The camshaft 42 is disposed between the intake and exhaust valves and across a position slightly deviated from the cylinder axis toward the intake valve. The left, right and center portions of the camshaft 42 are supported by left, right and center cam bearings, and the left and right cam bearings are formed on the mating surface of the cylinder head 13 at the lower left and lower right. It is composed of bearings 13d and 13f and left and right upper bearings (not shown) formed on the mating surface of the head cover 14. The center cam bearing 73 is mounted on the cylinder head 13
And a center upper bearing 14b formed at the center of the head cover 14.The center upper bearing 14b is connected to a right intake rocker arm 5 described later.
In order to avoid interference with the second boss portion 52c, it is slightly deviated from the cylinder axis to the left intake cam 42b side. Reference numeral 43 denotes a cam sprocket fixed to the left end of the cam shaft 42.

Here, the left, right, and center cam bearings are of a two-part type, and are constituted by fixing the head cover 14 to the cylinder head 13.
The opening edge, the respective cam bearings, and both edges of the plug insertion port 13 of the cylinder head 13 and the cylinder head 13 are fixed with fixing bolts (shown by hatching in FIG. 4). On the intake side of the opening peripheral portion, a flange portion 14h formed inside two places between the intake valves is fixed by fixing bolts 50b. In addition, this fixing bolt 50b
When the cap 57 is removed, it faces outward. Further, 50 of the fixing bolts is used for both the fixing and the rocker shaft detent described later. However, 50c is a non-rotating bolt.

Left and right exhaust rocker shafts 46a and 46b are disposed between the cam shaft 42 and the left and right exhaust valves 37 and 38 in parallel with the cam shaft 42, and are integrally formed on the inner surface of the head cover 14. It is supported by the bearing portion 14e and is prevented from rotating by the fixing bolt 50. The left and right exhaust rocker arms 47 and 48 are slidably supported by the left and right exhaust rocker shafts 46a and 46b. Each rocker arm 47, 48 is connected to the plug insertion hole 1
It is located on both sides of 3c, and is arranged in a C-shape with the camshaft side wider. Sliding portions 47a, 48a formed at the rear ends of the left and right exhaust rocker arms 47, 48 are provided on the left and right sides of the cam shaft 42, respectively.
Left and right exhaust cams 4 formed inside lower right cam bearings 13d and 13f
2a and 42d, and the lower end of an adjusting screw 49 screwed into the front ends 47b and 48b is connected to the left and right exhaust valve rods 37.
It is in contact with the upper ends of b and 38b.

Further, between the camshaft 42 and the intake valves 34 to 36, the left,
An intake rocker shaft 45 having a length extending over the right cam bearing is arranged in parallel with the cam shaft 42, and the rocker shaft 45 is supported at both ends and a central portion by bearings 14f formed integrally with the head cover 14, And it is stopped by the fixing bolt 50.
A left intake rocker arm 51 is rotatably supported on the left portion of the rocker shaft 45 from the center lower cam bearing 13e, and a center and right intake rocker arms 52 and 64 are swingably supported on the right portion, respectively. , 52, 64 are located between the left and right exhaust rocker arms 47, 48. A sliding portion 51a formed at the front end of the left intake rocker arm 51 is in sliding contact with a left intake cam 42b formed to the left of the center lower cam bearing 13e of the cam shaft 42, and is screwed into the rear end 51b. The lower end of the adjusting screw 53 is in contact with the upper end of the left intake valve rod 34b. Further, sliding portions 52a, 64a formed at the front ends of the center and right intake rocker arms 52, 64 are formed at the center and right intake cams 42 formed right next to the center lower cam bearing 13e of the cam shaft 42.
It is in sliding contact with c and 42e. The two intake rocker arms 52, 64
Adjusting screw 54, which is screwed into the rear end 52b, 64b
53 is in contact with the upper end of the center, right intake valve rod 35b, 36b.

The upper end of the central intake valve rod 35b is located at the left and right intake valve rods 34.
It is located above the upper ends of b and 36b when viewed in the cam axis direction, and is located rearward when viewed in the cylinder axis direction. That is, the plane projection distance l2 'from the rocker shaft 45 to the upper end of the valve rod 35b of the central intake valve 35 is longer than the plane projection distance 1' of the left and right intake valves 34, 36. Therefore, the arm length (vertical distance from the rocker shaft to the axis A) l2 of the central intake valve 35 is also longer than the arm length 1 of the left and right intake valves 34 and 36.

On the exhaust valve side of the head cover 14, two adjusting ports 14c for adjusting the adjusting screws 49 of the left and right exhaust valves 37 and 38 are formed, which can be opened and closed by separate caps 56. ing. One adjustment port 14d for adjusting the adjustment screws 53 and 54 of the intake valves 34 to 36 is formed on the intake valve side.
It can be opened and closed with two caps 57.

The two exhaust ports 28, 2 of the cylinder head 13
9. An interport jacket 77c is formed in a portion surrounded by the spark plug insertion hole 13c and the outer wall 13l. The port-to-port jacket 77c is located at the center of the exhaust ports 28, 29 when viewed in a state where the exhaust ports 28, 29 are sectioned in parallel with the camshaft and the cylinder, and the cylinder body 12
And extends upward from the 13m side of the mating surface to the vicinity of the top wall surface a of the exhaust ports 28, 29.

A pair of left and right communication passages 77b, 77b is formed between the mating surface 13m of the cylinder head 13 and the bottom surface b of the exhaust ports 28, 29. The communication passages 77b, 77b allow the inter-port jacket 77c to communicate with a main jacket 77a surrounding the upper surface of the combustion chamber 15. On the left intake port 22 side of the cylinder head 13, a main cooling water outlet 77g is formed, and the outlet 77g is connected to a radiator (not shown) by a cooling water hose (not shown).

On the mating surface 13 side of the cylinder head 13, cooling water inlets 77d, 77 for connecting the cooling jacket 12b of the cylinder body 12 to the communication passage 77b and the inter-port jacket 77c.
d ′ is formed.

And the cooling water inlet 77d 'of the jacket 77c between the ports.
Is mounted with a guide pipe 77i that forms a cooling water introduction passage. The guide pipe 77i is provided upright at the center as viewed in the direction perpendicular to the cam axis of the inter-port jacket 77c of the cylinder head 13, and the exhaust port
It extends near the center height of 28,29.

Since the guide pipe 77i is extended upward, the cooling water is introduced from the cylinder body 12 side into the upper part of the inter-port jacket 77c through the guide pipe 77i,
From the upper part, it descends along the side surfaces of the peripheral walls of the left and right exhaust ports 28, 29, flows through the left and right communication passages 77b, 77b to the main jacket 77a side, and exits the main cooling water outlet. Drained from 77g.

 Next, the operation and effect of this embodiment will be described.

In the engine of the present embodiment, the cooling water from the cooling jacket 12b of the cylinder body 12 flows from the cooling water inlet 77d to the communication passage 77b.
From the main jacket 77a
, Flows to the left intake port 22 side, is discharged from the main cooling water outlet 77g formed on the side, and is sent to the radiator. A part of the cooling water is supplied to the cooling water inlet 77d '.
Through the guide pipe 77i and into the upper part of the inter-port jacket 77c, where the upper part hits the ceiling wall 77h of the inter-port jacket 77c and reverses, along the sides of the peripheral walls of the left and right exhaust ports 28 and 29. To the main jacket 77a through the communication passage 77b,
Water is drained from the main cooling water outlet 77g formed on the side.

As described above, in the cooling structure of the present embodiment, the interport jacket 77c is provided at the portion surrounded by the exhaust ports 28, 29, the ignition plug insertion hole 13c, and the outer wall 13l.
And is formed so as to extend to near the top wall surface a of the exhaust ports 28 and 29, and a port-to-port jacket 77c is provided between the mating surface 13m and the bottom surface b of the exhaust ports 28 and 29. A pair of left and right communication passages 77b, 77b communicating with the main jacket 77a is formed, and a guide pipe 77i is erected at the center of the inter-port jacket 77c, and the guide pipe 77i is connected to at least the exhaust ports 28,29. Since the cooling water has been extended to the center height, the cooling water flows from the cylinder block 12 side through the guide pipe 77i and the port-to-port jacket 77c.
To the upper part of the exhaust port, and from the upper part, the left and right exhaust ports 2
It can be lowered along the side surfaces of the 8,29 peripheral wall and can flow to the main jacket 77a through the left and right communication passages 77b, 77b, so that cooling performance near the exhaust port and the spark plug insertion hole can be ensured.

Further, in this case, it is not necessary to provide a communication space between the exhaust port and the ignition plug insertion hole as in the above-described conventional structure, so that the exhaust ports 28 and 29, and thus the exhaust valves 37 and 38 can be increased in diameter. Higher speed and higher performance of the engine can be achieved.

In the above embodiment, the guide pipe 77i is attached as the cooling water introduction passage. However, the cooling water introduction passage may be formed integrally with the cylinder head as shown in FIGS. . In the drawings, the same reference numerals as those in FIGS. 1 and 2 denote the same or corresponding parts.

In the example of FIGS. 9 and 10, the interport jacket 77 is used.
A guide wall 77m as a cooling water introduction passage is integrally formed at the center of c. This guide wall 77m is for the left and right exhaust ports 2
Near the center height of 8,29 and the above port-to-port jacket 77c
The ceiling wall extends to around 77h.

Thereby, the cooling jacket 12b of the cylinder body 12
From the upper end opening of the guide wall 77m is introduced into the upper part in the jacket 77c between the ports, hits the ceiling wall 77h, reverses, descends along the side surfaces of the peripheral walls of the left and right exhaust ports 28, 29, It flows to the may jacket 77a side through the communication passage 77b.

〔The invention's effect〕

As described above, according to the cooling structure of the four-stroke engine according to the present invention, the inter-port jacket is positioned at the center of the portion surrounded by the two exhaust ports, the ignition plug insertion hole, and the outer wall, and the two exhaust ports are arranged at the center. A pair of left and right communication passages is formed between the mating surface and the bottom surface of the exhaust port so as to communicate with the main jacket, and a cooling water introduction passage is formed between the mating surface and the bottom surface of the exhaust port. Since the cooling water introduction passage is extended to at least the center height of the exhaust port at the center of the inter-port jacket, the cooling water flows from the cylinder body side through the introduction passage to the upper portion of the inter-port jacket. From the upper part, descends along the side surfaces of the left and right exhaust ports, and can flow into the main jacket through the left and right communication passages. , Cooling performance near the spark plug insertion hole can be ensured, and there is more space in terms of exhaust port formation compared to a structure in which a space is provided as a cooling water passage between the exhaust port peripheral wall and the ignition plug insertion hole peripheral wall. The diameter of the exhaust port can be increased, which has the effect of being able to cope with higher speed and higher performance of the engine.

[Brief description of the drawings]

1 to 8 are views for explaining a cooling structure of a four-stroke engine according to one embodiment of the present invention.
The figure is a sectional right side view of the cylinder head, and FIG. 2 is a view of FIG.
FIG. 3 is a cross-sectional plan view of the cylinder head, FIG. 4 is a plan view of the valve operating mechanism of the engine of the embodiment, FIGS. 5 and 6 are V-V in FIG. 7 is a bottom view of the cylinder head, FIG. 8 is a right side view of a motorcycle equipped with the engine of the embodiment, and FIG. 9 is a modified example of the embodiment. FIG. 10 is a cross-sectional view taken along the line XX of FIG. 9. In the figure, 10 is a 4-cycle engine, 12 is a cylinder body, 13 is a cylinder head, 13c is a spark plug insertion hole, 1
3l is the outer wall of the cylinder head, 28 and 29 are left and right exhaust ports, 42 is a cam shaft, 77c is a jacket between ports, 77d is a cooling water inlet, 77i and 77m are guide pipes and guide walls (cooling water introduction passages). is there.

Claims (1)

(57) [Claims] 1. An engine having two exhaust ports per cylinder and having an ignition plug insertion hole formed in a portion between the exhaust ports as viewed in a direction perpendicular to the camshaft, cools the vicinity of the ignition plug insertion hole and the exhaust port. In the cooling structure for the exhaust port, the two exhaust ports, the ignition plug insertion hole, and the portion surrounded by the outer wall of the cylinder head, when the exhaust port is viewed in a cross section parallel to the camshaft and the cylinder axis, the two exhaust ports A port-to-port jacket is formed so as to be located at the center of the port and to extend upwardly from the mating surface with the cylinder body to at least near the top wall surface of the two exhaust ports, and Forming a pair of left and right communication passages between the bottom surface and the main jacket surrounding the combustion chamber;
A cooling water introduction passage opening at the mating surface of the cylinder head is erected at the center of the inter-port jacket, and the cooling water introduction passage is extended to at least the center height of the exhaust port, so that the cooling water flows from the cylinder head side. Introduced into the upper part of the inter-port jacket through the cooling water introduction passage,
A cooling structure for a four-stroke engine, wherein the cooling structure descends from the upper part along side surfaces of the left and right exhaust ports, and flows to the main jacket through the left and right communication passages.